A three-story office building designed by the APA Wojciechowski Architekci team is under construction in Wielu near Koscierzyna. In this case, the choice of CLT technology was natural, as the investor is a manufacturer of wood, and the building will be its business card - even the elevator shaft in it is made of wood! We talk to Magdalena Rach uta and Ewa Sroczynska, the architects in charge of the Kashubian project, about what can and cannot be built with CLT, the challenges of designing this type of construction, and whether it really is a faster process.
Magdalena Rachuta - architect, associated with APA Wojciechowski Architekci studio since 1994. A graduate of the Faculty of Architecture at the Warsaw University of Technology, she also completed postgraduate managerial studies at the Warsaw School of Economics. Since 2015, she has been discovering the secrets of buildings with CLT construction.
Ewa Sroczynska - architect, since 2021 she has been associated with APA Wojciechowski Architekci. She received her education, studying at the Faculties of Architecture in Poland (graduated from the Cracow University of Technology), Spain and the United States. She gained professional experience in design offices in Japan (Isozaki, Aoki & Associates / AAarchitects), Canada (Chris Doray Studio) and the United States (SHO Architecture).
Ola Kloc: The building is being constructed as a showcase for a wood manufacturer. In this case, the choice of CLT (cross-laminated timber) technology was obvious. Still, it is not a natural choice among investors of office buildings - why?
Magdalena Rachuta: This is due to the absence of wood as a modern construction material on the market. It's all just in its infancy. For years I've been going to conferences on this topic, where everyone is enthusiastic, but beyond this enthusiasm not much is happening. But we are starting and trying, we have to learn it. We are also aware of the approaching dates when construction will have to be zero-emission [from 2030 all new buildings in the European Union are to be zero-emission, and two years earlier all new buildings occupied or owned by public authorities are to meet this condition - editor's note].
Ola Kloc: What could be the reason for this blockage in the creation of wooden buildings?
Magdalena Rachuta: This is a relatively new technology, I'm not talking about glulam, because we have had these elements for a long time. I think it takes time.
bird's eye view
VIS. Adam Kaminski © APA Wojciechowski Architects
Ola Kloc: Regulations allow the use of wood. So is it a matter of investors or architects breaking through?
Magdalena Rachuta: Both sides. We have to learn this material. The building of the Sylva company in Many is our sixth wooden project - unfortunately, the previous ones, for various reasons, were suspended, but the knowledge gained during their creation is priceless. I've been designing office buildings for twenty years, and I thought it was possible to just switch from reinforced concrete to wood, but not really. You have to learn all these nuances, to feel, first of all, the dimensions of the elements, to be able to use them freely afterwards.
Ola Kloc: Did you face any challenges in this case, in terms of building, fire regulations?
Ewa Sroczynska: The biggest challenge, so far, is fire regulations. Polish technical conditions do not distinguish CLT technology - they treat a wood building and a building made of cross-laminated timber the same way. And the difference is fundamental. CLT may have very good fire resistance parameters, but by being systematized on a par with wood, it is considered as the same combustible material. And this causes concern - we think wood is about to burn. Until CLT is treated by regulations as a separate building and construction material, and its fire resistance is approved as sufficient, the use and application of this material will continue to be limited.
Magdalena Rachuta: Open-minded firefighters are looking for solutions, unfortunately not all of them, and sometimes we hear concerns - because, after all, "it burns."
The project in Many is an example of the purity of the use of CLT wood and its use to maximum
vision. Adam Kaminski © APA Wojciechowski Architects
Ola Kloc: How do you try to convince such fire-minded people?
Magdalena Rachuta: With conversation. We meet all the provisions of technical conditions, each element is designed according to Eurocode, has the required parameters of R, EI, which is no longer disputed. Since we meet all the provisions of the law, we ask: "Why not?".
Ola Kloc: Are there any elements of construction that cannot be made with CLT?
Magdalena Rachuta: Fire separations must be made of non-combustible materials.
projections
© APA Wojciechowski Architects
Ola Kloc: How did you solve this in Many?
Magdalena Rachuta: In this project there is one fire zone, so we were in a very comfortable situation. But we also have such a project behind us, which, due to the two ZL [human risk - editor's note] categories in the building, we had to divide into two zones - so we used a masonry wall. The building had a convenient form for division, and there was no architectural or functional problem with it. Everyone asks why we are designing undersized buildings for now. The main issue is precisely the fire zones. In large buildings, individual floors can be one zone, so both the ceiling and what it supports must be made of noncombustible materials.
We recently spoke with a developer of large buildings and speculated on what CLT wood elements we could "put" in such office buildings.
cross sections
© APA Wojciechowski Architects
Ola Kloc: How is this idea promising?
Magdalena Rachuta: The willingness is promising! And as for the technical limitations, we already have to sit down together and somehow work them out. More and more investors would like to use wood.
Ola Kloc: The building in Many is largely glazed - how did you take care of thermal comfort inside?
Magdalena Rachuta: This is always a problem of aesthetics, when we want to make a light and transparent building, and on the other hand - the amount of sun heats up our interior. We then rely on air-conditioning systems and carefully selected glazing parameters. In this project, we didn't use any external shading elements so as not to obscure the wooden structure. We wanted to maintain a minimalist enclosure.
Ewa Sroczynska: In CLT's wood solutions, the dimensions of the structural elements are larger than in reinforced concrete. And although we didn't use any external shutters in our design, and the building is enclosed with a glass facade, we took advantage of the size of the structural columns - by spacing them appropriately, they create a kind of internal shutter and prevent the building from getting too hot. What is a disadvantage with CLT wood structures, i.e. larger cross-sections of structural elements, we used to ensure that the building is protected from too much sunlight.
Magdalena Rachuta: The columns are set every 140 centimeters, duplicating the facade pillars. We even prepared a simulation for our client, which showed how these pillars would shade the interior, and proved that he wouldn't need anything else, because the amphillade of 50-centimeter pillars creates such an effect.
The building is being constructed as a showcase for a wood manufacturer - so the choice of CLT technology was a natural one
© APA Wojciechowski Architects
Ola Kloc: The building is to be not only a showcase for the company, but also a model building for the entire industry. This is quite a challenge - what solutions used in this project are worth imitating in the future?
Magdalena Rachuta: An example is the "inverted" ceiling-to-ceiling layout, which was actually a suggestion from the client. In the original concept, the installations were visible under the ceiling, but the investor said he didn't want such an aesthetic mess, and asked us to keep the ceiling empty. So all the installations serving the floor below are located under the raised floor of the floor above, meaning our ceiling is exposed and forms the ceiling of the room. This is a big coordination challenge, but we managed, and we will see what the result will be.
Ewa Sroczynska: The investor wanted to expose the CLT wood as much as possible, which was an interesting challenge for us - to see to what extent we can use this construction material as a finishing material. We created, for example, the first wooden elevator shaft in Poland.
Magdalena Rachuta: Because of the building's category, which changed during the design process, the staircase runs had to be reinforced concrete. Initially they were also wooden, so we had an all-wood building.
The project in Many is an example of using CLT technology to the maximum, even the elevator shaft is wooden
© Fort Poland
Ola Kloc: Do you feel the differences in the design process depending on the technology?
Magdalena Rachuta: The difference is what Ewa mentioned, that is, the dimensions of the structural elements and the ceiling, which is not flat. What is natural in reinforced concrete, we have a 25-centimeter slice and we're done, here it doesn't work like that - the elements have to support themselves on something, on a beam, which - depending on the span and structural layout - is 60, 70, 80 or 90 centimeters. This is a complicated issue. Installations are also a challenge, as they can pass through structural elements to a limited extent. The openings must be established, calculated, checked. The process of coordinating installation and construction in a project is longer, more detailed.
Ola Kloc: What was the schedule for the project and implementation? When did construction begin and at what stage is it now? How much time did the whole process take? Does detailed preparation mean faster implementation?
Magdalena Rachuta: With prefabrication, everyone says it's a faster process - the construction itself definitely is, but considering the design, preparation and production of the elements - I think the time is similar. In Many, the design process was split into two phases, halted during the pandemic. So it's hard to say how long it took. Construction itself began in the spring of 2024, and we already have the building closed [as of December 2024 - editor's note]. The facility is scheduled for completion in the first months of 2025. The big time savings will be in the finishing stage, so I think it will actually be a faster process.
Ewa Sroczynska: Due to the fact that CLT itself is a finishing material, work with the detailing was already carried out at the concept stage. In fact, there was no standard division here: concept, structural design, detailed design, because from the very beginning we had to think about what we wanted to show and how we wanted to show it, for example, what will be the consequences of choosing such or such a different span in the building on the floor slab layout visible to the users.
Magdalena Rachuta: The constructors are designing interior elements for us, something they were not fully aware of at first. This is a novelty for both parties.
The project was a challenge for the team - to see to what extent CLT could be used
© Fort Poland
Ola Kloc: Because these are prefabricated elements, don't you feel limited in creating your architectural vision?
Magdalena Rachuta: I like simple forms.
Ewa Sroczynska: It is a greater challenge, but also greater satisfaction that while maintaining modularity we are able to offer interesting solutions.
Magdalena Rachuta: In fact, thanks to the exposure of wood, we always have a warm interior, "smelling of Christmas", regardless of the form [laughter].
Ola Kloc: Did you take into account such things as the carbon footprint of the building in this project?
Magdalena Rachuta: For research purposes, we developed together with Buro Happold a comparison of the building in Many and an analogous reinforced concrete building. CLT comes out much better in this comparison. Everyone asks us about the cost - which will be cheaper. Szymon [Wojciechowski - editor's note] always says that we would have to build twins with different technologies and then we will know which costs more. And when it comes to the carbon footprint, we also have to keep in mind the use of that wood later, it accumulatesCO2 very nicely as long as it is wood.
Ola Kloc: Does the project plan for the possible removal of wooden elements in the future?
Magdalena Rachuta: Usually such analyses are done for certifications, which also include the "death of the building."
Ewa Sroczynska: For now, probably, there will be thoughts of expansion.
stages of construction
© Fort Poland
Ola Kloc: How do you see the future of wood technologies in Polish architecture?
Magdalena Rachuta: We are keeping our fingers crossed and watching how this pebble thrown in the water forms wider and wider circles. We hope to start talking about it more widely, because so far in the projects we've done, it was something natural for investors. We've designed in-house offices for companies that are in an industry somehow related to wood or innovation. I think it's only zero carbon that will awaken the need for wood.
Ola Kloc: Do the companies you have worked with take into account this future production of wood - its greater consumption will require more production, i.e. more trees.
Magdalena Rachuta: We architects do not work directly with such companies during the design process, but when it comes to wood production in Poland, there is a light at the tunnel - eight years ago at the first Holzbau conference I listened to speakers who said that in Poland we do not produce wood for CLT material. Now I can already hear that such activities have begun.
Ewa Sroczynska:The project in Many is an example of the purity of the application of CLT wood and its use to the maximum, but it is a small facility. Moving to a larger scale, or thinking about the development market, it seems to me that it is more common sense to talk not so much about whole buildings with CLT, but hybrid buildings. Given the size of the structural dimensions or the amount of wood used, we should use cross-laminated timber in a thoughtful way. Designing hybrid buildings seems to be a responsible solution.
Magdalena Rachuta: For example, sections or the top floors of tall buildings, could be built with CLT. There are also often extended first floors that have pavilion-like forms - why not use CLT there? We need a green light for this material to begin to exist in the space.
Ola Kloc: Such solutions can also tame and show the possibilities of the material. As architect Dominika Zielinska said during last year's Architecture Weekend in Gdynia, we can experiment on a small scale and bit by bit. Thank you for the interview!
interviewed by Ola Kloc
Illustrations courtesy of APA Wojciechowski Architekci studio
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